RT-20 Edge Cases - Release Testing

Edge cases: metadata issues, outlier layers, two-map pages, error layer reload, overlays, sandbox, responsive layout.

Test plan: 20-edge-cases.md

outlier-metadata.html — Metadata edge cases (nameField=Date, empty entries, WMS with space/slashes in ID)
demo-circumpolar.html — Circumpolar config (EPSG:3573)